It is well known in the tube welding process that metal strip is formed into a circular cross-section with opposing strip edges facing each other. The faces of these edges are heated to a plastic state and immediately pressed or, forged together forming a welded tube. During the pressing or, forging action the surface scale and a small portion of the parent strip metal is extruded both upward and downward simultaneously from the weld area. This extruded metal, commonly referred to as upset, is removed immediately after welding.
During the pressing, or forging action the extrusion or, upset on the inside of the tube is often at a sufficiently high temperature that small portions of the upset drip away from the extrusion. This drippage, while falling to the bottom of the welded tube, assumes a spherical shape. This drippage is quenched into the spherical shape or, beads by the liquid coolant in the bottom of the welded tube. These beads of drippage, commonly referred to as splatter, are carried along the bottom of the welded tube by the movement of the tube and entrapped liquid coolant.
Immediately following welding the tube travels to upset removal stations. Here both the outside and inside upsets are removed with carbide or ceramic metal cutting tools. The inside cutting tool is generally nested in a holder which rides on and/or is guided with rollers mounted on top and bottom of the holder. The bottom rollers of this holder is forced against the bottom inside surface of the tube by mechanical or hydraulic means forcing the holder to rise until the top rollers ride against the top inside surface of the tube. These top rollers are grooved and straddle the weld upset. The inside contained cutting tool is oriented with the top rollers to remove the upset to the original wall thickness. See U.S. Pat. No. 4,682,921 which discloses an internal upset removal station.
Since the beads of splatter are moving along the bottom inside surface with the welded tube, they are rolled into the bottom surface of the tube by the rolling action of the bottom rollers against the bottom surface of the welded tube. This rolled-in splatter is considered a blemish in some tube applications, i.e., tubing for hydraulic or air cylinder usage, and is a cause for rejection of the tube.